Chemical mechanical polishing pad having holes and or grooves

ABSTRACT

Disclosed is a chemical mechanical polishing pad formed with holes, grooves or a combination thereof. The chemical mechanical polishing pad is characterized in that a plurality of concentric circles each having grooves, holes, or a combination thereof are formed at a polishing surface of the polishing pad. The chemical mechanical polishing pad provides effects of effectively controlling a flow of slurry during a polishing process, thereby achieving a stability in the polishing process in terms of a polishing rate, and achieving an enhancement in the planarization of a wafer.

TECHNICAL FIELD

[0001] The present invention relates to a polishing pad used in achemical mechanical polishing process, and more particularly to achemical mechanical polishing pad formed at a polishing surface thereofwith a plurality of concentric circles each having grooves, holes, or acombination thereof.

BACKGROUND ART

[0002] Generally, chemical mechanical polishing (CMP) is a highprecision/mirrored surface polishing method used to obtain globalplanarization in a semiconductor device manufacturing process. Inaccordance with such CMP, a slurry is supplied between a polishing padand a wafer to be polished, so as to chemically etch the surface of thewafer. Using the polishing pad, the etched surface of the wafer ismechanically polished.

[0003] Referring to FIG. 1, a typical CMP machine, which is denoted bythe reference numeral 1, is schematically illustrated. Also, a CMPmethod using the CMP machine 1 is schematically illustrated in FIG. 2.The CMP method includes a chemical etching reaction process and amechanical polishing process, which are conducted using a polishing pad10 included in the CMP machine 1. The chemical etching reaction iscarried out by a slurry 42. That is, the slurry 42 serves to chemicallyreact with the surface of a wafer 30 to be polished, thereby making itpossible for the mechanical polishing process, following the chemicaletching reaction, to be easily carried out. In the mechanical polishingprocess, the polishing pad 10, which is fixedly mounted on a platen 20,rotates. The wafer 30, which is firmly held by a retainer ring 32,rotates while oscillating. A slurry containing abrasive particles issupplied to the polishing pad 10 by a slurry supply means 40. Thesupplied slurry is introduced between the polishing pad 10 and the wafer30. The introduced abrasive particles come into frictional contact withthe wafer 30 by virtue of a relative rotating speed difference betweenthe polishing pad 10 and the wafer 30, so that they conduct mechanicalpolishing. The slurry 42 is a colloidal liquid containing abrasiveparticles having a grain size of nanometers. This slurry 42 is spread onthe polishing pad 10 during the polishing process. As the polishing pad10 rotates during the polishing process, the slurry 42 supplied to thepolishing pad 10 is outwardly discharged from the periphery of thepolishing pad 10 due to a centrifugal force caused by the rotation ofthe polishing pad 10. In order to achieve an enhanced polishingefficiency, many abrasive particles should remain for a desirablelengthy period of time on the upper surface of the polishing pad 10 sothat they. participate in the polishing of the wafer. That is, thepolishing pad 10 should make the slurry 42 be held on the surfacethereof for as long a period of time as possible.

[0004] Centrifugal force generated during the rotation of the CMP pad ishigher at a position nearer to the periphery of the polishing pad. Dueto such a centrifugal force difference between different radialpositions on the polishing pad, the slurry on the polishing pad exhibitsan increased flow rate as it approaches the periphery of the polishingpad. Thus, the slurry is non-uniformly distributed in the radialdirection of the polishing pad. Due to such a non-uniform distributionof the slurry, the wafer is non-uniformly polished because its polishingrate is varied depending on a radial position of the polishing pad incontact with the wafer's surface. Such a variation in polishing rateaffects the planarization of the wafer. As a result, the polishing padexhibits a considerable difference in polishing rate between its centralportion and its peripheral portion. For this reason, it is necessary touniformly distribute the slurry over the polishing pad by controllingthe flow of slurry on the polishing pad.

[0005] During the polishing process, the wafer is pressed against thepolishing pad so that it comes into frictional contact with abrasiveparticles. Due to this pressure, however, it may be difficult for theslurry to reach the central portion of the wafer. For this reason, theslurry may be distributed at the central portion of the wafer in arelatively reduced amount, as compared to the amount at the peripheralportion of the wafer. As a result, the wafer is non-uniformly polished.

[0006] In order to solve such a problem, a method has been proposed, inwhich holes or grooves having a desired width, depth and shape areformed on a CMP pad. Such holes or grooves act to control the flow anddistribution of the slurry continuously supplied during the polishingprocess.

[0007] Now, holes or grooves conventionally formed on a polishing padwill be described in conjunction with the annexed drawings.

[0008]FIG. 3a is a schematic view illustrating a polishing pad formedwith grooves respectively having the form of concentric circles. FIG. 3bis a cross-sectional view taken along the line A-A of FIG. 3a. As shownin FIGS. 3a and 3 b, the grooves formed on the polishing pad have theform of concentric circles uniformly spaced apart from one another in aradial direction while having different diameters, respectively. Theslurry, which is continuously supplied onto the polishing pad, is forcedto move outwardly by a centrifugal force generated as the polishing padrotates. As a result, during the polishing process, the slurry istemporarily collected in the concentric circular grooves, and thenoutwardly discharged from those grooves. An example of such concentriccircular grooves is disclosed in U.S. Pat. No. 5,984,769. This U.S. Pat.No. 5,984,769 discloses a polishing pad formed with a plurality ofconcentric circular grooves or spiral grooves. The polishing pad isdivided into a plurality of groove regions where grooves havingdifferent widths and different lengths are formed, respectively.However, such a polishing pad having circular or spiral grooves cannotmeet various conditions required in a CMP process because it has a fixedpattern formed only of grooves.

[0009]FIG. 4a is a schematic view illustrating a polishing pad formedwith holes having a conventional structure. FIG. 4b is a cross-sectionalview illustrating holes shown in FIG. 4a. In the polishing pad of FIG.4a, a plurality of holes are regularly arranged. The holes arranged onthe polishing pad store a slurry supplied thereto, thereby retarding adischarge of the stored slurry caused by centrifugal force. U.S. Pat.No. 5,853,317 discloses a polishing pad formed with grooves at a firstsurface thereof serving as a polishing surface to polish an object andgrooves at a second surface fixedly mounted to a platen in such afashion that the grooves formed at the second surface have a larger sizethan the grooves formed at the first surface. Also, U.S. Pat. No.5,329,734 discloses a polishing pad having a first region formed with aplurality of pores and a second region formed with a plurality ofopenings.

[0010] In the case of the conventional polishing pad having grooves orholes uniformly spaced apart from one another, the slurry supplied ontothe polishing pad is hindered from flowing toward the central portion ofa wafer being polished at regions where the polishing pad is in contactwith the wafer. As a result, a degradation in polishing rate occurs atthe central portion of the wafer.

[0011] On the other hand, in the case of the conventional polishing padhaving concentric circular grooves, a superior slurry storage capacityis obtained because each groove has a partially closed structure havingvertical groove walls capable of retaining the slurry in the grooveagainst centrifugal force, as compared to other conventional polishingpads. However, this polishing pad has a drawback in that each groove hasan insufficient depth corresponding to ¼ of the thickness of thepolishing pad.

[0012] Since the grooves or holes formed on the above mentionedconventional polishing pads have a fixed pattern such as concentriccircles or a lattice, it is difficult to form a groove pattern capableof effectively controlling the flow of a slurry. In accordance with themethod for forming perforations using perforating pins, the perforationshave a fixed shape. Since the holes have a simple and fixed pattern, itis difficult to arrange them to have diverse hole patterns desired in aCMP process.

[0013] In order to solve such problems, accordingly, it is necessary todesign the shape, density and distribution of grooves or holes, takinginto consideration the given polishing process conditions such ascentrifugal force and wafer position.

DISCLOSURE OF THE INVENTION

[0014] Therefore, an object of the invention is to provide a CMP pad fora CMP process which is formed with holes, grooves or a combinationthereof capable of retarding the discharge rate of a slurry suppliedonto a polishing surface while uniformly distributing the slurry overthe polishing surface.

[0015] Another object of the invention is to provide a CMP pad formedwith holes, grooves or a combination thereof capable of effectivelycontrolling the flow of a slurry supplied onto the polishing pad duringa CMP process.

[0016] In accordance with the present invention, these objects areaccomplished by providing a CMP pad used for a CMP process, wherein aplurality of concentric circles each having grooves, holes, or acombination thereof are formed at a polishing surface of the pad.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a schematic view illustrating the configuration of atypical CMP machine and a polishing method performed using the CMPmachine;

[0018]FIG. 2 is a schematic view illustrating the concept of a CMPmethod;

[0019]FIG. 3a is a schematic view illustrating a polishing pad formedwith grooves respectively having the form of concentric circles;

[0020]FIG. 3b is a cross-sectional view taken along the line A-A of FIG.3a;

[0021]FIG. 4a is a schematic view illustrating a polishing pad formedwith holes having a conventional structure;

[0022]FIG. 4b is a cross-sectional view illustrating holes shown in FIG.4a;

[0023]FIG. 5 is a schematic view illustrating diverse shapes of grooves,holes or combinations thereof formed in accordance with the presentinvention;

[0024]FIGS. 6a to 6 d are schematic views illustrating various examplesof a concentric circle formed by grooves, holes, or a combinationthereof, respectively;

[0025]FIG. 7 is a schematic view illustrating a polishing pad having aplurality of concentric circles of different diameters each composed ofa plurality of holes;

[0026]FIG. 8 is a schematic view illustrating a polishing pad which isdivided into two radial regions each having a plurality of concentriccircles of different diameters each composed of a plurality of holes;and

[0027]FIGS. 9 and 10 are schematic views respectively illustrating CMPpads each having a plurality of concentric circles of differentdiameters each composed of grooves, holes, or a combination thereof.

BEST MODE FOR CARRYING OUT THE INVENTION

[0028] Now, the present invention will be described in detail in termsof its constitution and function, with reference to the annexeddrawings.

[0029] In accordance with the present invention, a CMP pad is providedwhich has, at a polishing surface thereof, a plurality of concentriccircles each having grooves, holes, or a combination thereof. Referringto FIG. 5, diverse shapes of such grooves, holes or combinations thereofarranged in the form of a concentric circle in accordance with thepresent invention are illustrated.

[0030] In accordance with the present invention, continuous grooves eachhaving a desired width and a desired depth may be formed to have theform of concentric circles, respectively. Such continuous grooves aredisclosed in U.S. Pat. No. 5,984,769. In the case of a polishing paddisclosed in U.S. Pat. No. 5,984,769, a plurality of uniformly spacedconcentric circular grooves are formed.

[0031] In accordance with the present invention, discontinuous grooveseach having a desired width, depth and length may be formed which areregularly arranged while being spaced apart from one another. Thesegrooves may be uniformly spaced apart from one another by apredetermined distance. Alternatively, the grooves may be regularly orirregularly arranged while being uniformly or non-uniformly spaced apartfrom one another. Also, the grooves may have different depths, widths,or lengths, respectively. Typically, each groove may have a rectangularcross-sectional shape. Of course, each groove may have othercross-sectional shapes, for example, an inverted triangular shape.

[0032] Alternatively, a plurality of holes, which have a desired depthand diameter, may be arranged to have a uniform space between thecenters of adjacent ones thereof in accordance with the presentinvention. Where the space between adjacent holes is smaller than radiusof the holes, the holes have a continuous arrangement. The space betweenadjacent holes can be adjusted to be increased or reduced. In addition,the polishing pad of the present invention may have hole groups eachhaving at least two holes spaced apart from each other by a distance ofr1. In this case, the hole groups may be regularly arranged while beinguniformly spaced apart from one another by a desired distance of r2(r2>r1). In this case, the holes may also be non-uniformly spaced apartfrom one another, as in the grooves. Also, the holes may have differentdepths, diameters, or shapes, respectively.

[0033] In accordance with the present invention, a combination of holesand grooves may be formed. The combination of holes and grooves mayinclude combinations of grooves and holes having diverse patterns. Thatis, the polishing pad of the present invention may have a number ofdifferent patterns each formed by a combination of holes and grooves.For example, holes each having a desired depth and diameter and grooveseach having a desired depth, width, and length may be alternatelyarranged while being spaced apart from one another.

[0034] Each pattern formed by grooves, holes or a combination thereofforms a concentric circle. Various examples of such a concentric circleformed by grooves, holes, or a combination thereof are illustrated inFIGS. 6a to 6 d, respectively.

[0035]FIG. 6a shows a concentric circle formed by a plurality of grooveshaving a desired width and length while being uniformly spaced apartfrom one another. FIG. 6b shows a concentric circle formed by aplurality of holes having a desired width and length while beinguniformly spaced apart from one another. FIGS. 6c and 6 dshow concentriccircles each formed by a combination of grooves and holes, respectively.In the concentric circle of FIG. 6c, grooves and holes are regularlyarranged in such a fashion that one groove alternates with one holewhile being uniformly spaced apart from one another. In the concentriccircles of FIG. 6d, grooves and holes are regularly arranged in such afashion that two holes alternate with one groove while being uniformlyspaced apart from one another.

[0036] The concentric circles respectively shown in FIGS. 6a to 6 d areonly for illustrative purposes. In accordance with the presentinvention, it is possible to form concentric circles having diversepatterns each composed of holes, grooves or a combination thereof havingdiverse shapes.

[0037] Thus, the CMP pad of the present invention may be formed with aplurality of concentric circles of different diameters each havinggrooves, holes, or a combination thereof.

[0038] In accordance with the present invention, the concentric circlesformed on the polishing pad may have identical or different patternseach composed of grooves, holes, or a combination thereof. Also, theconcentric circles may have the same pattern at a certain region of thepolishing pad while having different patterns at other regions.

[0039] The space between adjacent concentric circles formed on thepolishing pad may be uniform or nonuniform. Also, the circle space mayvary gradually in accordance with the circle radius. For example, thecircle space may be gradually reduced from the central portion to theperipheral portion of the polishing pad while being inverselyproportional to an increase in circle radius.

[0040]FIG. 7 illustrates a polishing pad formed with a plurality ofconcentric circles of different diameters each having a plurality ofholes. In this case, the holes of the concentric circles have the samediameter and the same hole space. The concentric circles also have thesame circle space. Of course, various modifications are possible byadjusting the depth, diameter, or space of the holes forming eachconcentric circle or the circle space, thereby varying the hole patternof the polishing pad.

[0041] In accordance with the present invention, the polishing pad maybe divided into a plurality of radial regions. Referring to FIG. 8, apolishing pad is illustrated which is divided into two radial regions.

[0042] Each radial region of the polishing pad may be formed with aplurality of concentric circles having different diameters while havingthe same pattern. The radial regions may have different patterns ordifferent depths, widths or spaces of grooves or holes.

[0043] For example, the polishing pad may be divided into inner andouter radial regions respectively defined at opposite sides of a circlehaving a radius r₀. The inner radial region has a radius smaller thanthe radius r₀ (r<r₀) whereas the outer radial region has a radius largerthan the radius r₀(r>r₀). Each of the inner and outer radial regions isformed with concentric circles having different radii while beingcomposed of holes having the same diameter and the same hole space. Theouter radial region may have a larger hole diameter and hole space thanthose of the inner radial region.

[0044]FIGS. 9 and 10 illustrate embodiments of the present inventionassociated with CMP pads each formed with a plurality of concentriccircles of different diameters having grooves, holes, or a combinationthereof.

[0045] In either case, holes and/or grooves can be formed to havediverse patterns capable of optimally meeting the given polishingprocess conditions.

[0046] Preferably, the formation of holes, grooves or a combinationthereof is achieved using a laser machining process. The laser machiningprocess provides advantages in that it is capable of precisely machiningholes or grooves having a complicated structure, making the holes and/orgrooves have a smooth inner surface, and easily adjusting the shape,size, and depth of the holes and/or grooves.

[0047] Of course, the machining of holes, grooves or a combinationthereof may be achieved by a cutting or milling process using mechanicalmeans in accordance with the present invention. Also, the machiningprocess may be achieved using a combination of a laser machining methodand a mechanical machining method.

[0048] Industrial Applicability

[0049] As apparent from the above description, the present inventionprovides a polishing pad for a CMP process which is formed with holes,grooves or a combination thereof having diverse shapes, sizes, andpatterns while being capable of retarding the discharge rate of a slurrysupplied onto a polishing surface, uniformly distributing the slurryover the polishing surface, and effectively controlling the flow of theslurry during the CMP process, thereby stably maintaining a desiredpolishing rate and achieving an improved planarization.

[0050] Although the preferred embodiments of the invention have beendisclosed for illustrative purposes in conjunction with a hole and/orgroove pattern formed on a polishing pad used in a CMP process, thoseskilled in the art will appreciate that various modifications, additionsand substitutions are possible, without departing from the scope andspirit of the invention as disclosed in the accompanying claims.

1. A chemical mechanical polishing pad used for a chemical mechanicalpolishing process, wherein a plurality of concentric circles each havinggrooves, holes, or a combination thereof are formed at a polishingsurface of the pad.
 2. The chemical mechanical polishing pad accordingto claim 1, wherein each of the concentric circles has a plurality ofdiscontinuous grooves arranged to be spaced apart from one another, eachof the grooves having a desired depth, a desired width, and a desiredlength.
 3. The chemical mechanical polishing pad according to claim 2,wherein the grooves are different in at least one of their depth, width,and length.
 4. The chemical mechanical polishing pad according to claim2, wherein the space defined between adjacent ones of the grooves isuniform or non-uniform.
 5. The chemical mechanical polishing padaccording to claim 1, wherein each of the concentric circles has aplurality of holes arranged to be spaced apart from one another, each ofthe holes having a desired depth and a desired diameter.
 6. The chemicalmechanical polishing pad according to claim 5, wherein the holes aredifferent in at least one of their depth, their diameter, and theirspace defined between adjacent ones thereof.
 7. The chemical mechanicalpolishing pad according to claim 1, wherein each of the concentriccircles has a combination of holes having a desired depth, a desireddiameter, and a desired space defined between adjacent ones thereof andgrooves having a desired depth, a desired width, and a desired length,the holes and grooves being alternately arranged while being spacedapart from one another to alternate at least one of the holes with oneof the grooves.
 8. The chemical mechanical polishing pad according toany one of claims 1 to 7, wherein the concentric circles are uniformlyspaced apart from one another.
 9. The chemical mechanical polishing padaccording to any one of claims 1 to 7, wherein the concentric circlesare non-uniformly spaced apart from one another so that the spacedefined between adjacent ones of the concentric circles is graduallyreduced from a central portion of the pad to a peripheral portion of thepad.
 10. The chemical mechanical polishing pad according to any one ofclaims 1 to 7, wherein the grooves, holes, or combination thereof aremachined by a laser.
 11. A chemical mechanical polishing pad used for achemical mechanical polishing process, the pad being divided into atleast two radial regions each formed with a plurality of concentriccircles of different diameters having the same pattern of grooves, holesor a combination thereof, the pattern of each of the radial regionsbeing different from the patterns of the remaining radial regions.
 12. Achemical mechanical polishing pad used for a chemical mechanicalpolishing process, the pad being divided into at least two radialregions each formed with a plurality of uniformly spaced concentriccircles of different diameters each having grooves, holes or acombination thereof, the space between adjacent ones of the concentriccircles in each of the radial regions being different from those of theremaining radial regions.